Reel mowers use a scissoring action to shear grass and like foliage, rather than tearing the leaves as with a conventional rotary mower. Because the shearing action leaves a neatly cut top end to the grass, compared to the torn end common with rotary cutters, the grass has an improved appearance. Such reel mowers are more expensive and require more maintenance than rotary mowers, however they are preferred by golf courses and the like where appearance and healthy grass are important. Individual reel mower assemblies are quite narrow, and consequently reel mower units commonly comprise a plurality of side-by-side reel mower assemblies.
Examples of such mowers are disclosed in U.S. Pat. Nos. 5,291,724, 5,477,666 and 6,318,059 to Cotton. In a typical reel mower assembly, the mower frame comprises fixed side plates and an attachment member, commonly called a bed bar, fixed to the frame and extending from one side of the frame to the other. A replaceable bed knife is attached to the bed bar, and a reel head with helical knives mounted thereon is rotatably mounted in each side plate of the frame and extends across the mower assembly above the bed knife. The reel head and bed knife are oriented such that the bed knife is parallel to the reel axis and in close proximity to the reel knives as the reel head rotates so that a shearing action is achieved between the reel knives and the bed knife. Typically an adjustment mechanism is provided to allow movement of the bed bar relative to the reel head so that the bed knife can be moved into proper relationship with the rotating reel knives.
Height of cut control is also provided to maintain the bed knife at a constant vertical position with respect to the grass so that the cut grass is substantially all the same height. Typically front and rear ground rollers are rotatably mounted in each side plate of the frame and extend across the assembly, one forward of the bed knife and one rearward. The ground rollers are lower than the bed knife and support the assembly as it rolls across the ground. The ground rollers can be moved up and down to adjust the vertical position of the bed knife with respect to the ground and thus the cutting height.
Conventionally the reel head comprises a shaft extending through bearings in each side plate of the frame. A drive sprocket, pulley, or the like is attached to one end of the shaft outside the side plate, and a chain, belt, or like drive mechanism is connected to rotate the reel. Removing the reel head for replacement or repair thus requires considerable disassembly, such as removal of bearings, pulleys, and the like from the shaft to allow removal of the reel.
The reel head is also susceptible to damage when a rock or like object becomes jammed between the bed knife and one of the reel knives, since conventionally the reel head and bed knife are fixed to the frame, and so neither can move in response to the force of a jammed object.
U.S. Pat. No. 6,889,491 to the present inventor Buchko discloses a magnetic bed knife attachment to facilitate removal and replacement of the bed knife. Instead of a plurality screws, the bed knife is attached to the bed bar with magnets such that same can be readily removed for sharpening, repair, replacement, and like maintenance. Also, where the force exerted by a jammed rock or like obstruction is sufficient, the bed knife of Buchko will be forced away from the bed bar, thus avoiding or at least reduce damage to the bed knife and the reel knives. Damage to the reel head can still occur however if, for example, the object jams between the bed bar, which is still rigidly attached to the frame, and the reel knives.